Apparatus for fluidically controlling the assembly and dynamic resistance adjustment of acoustic resistors

ABSTRACT

A method of and apparatus for fluidically controlling the sensing, staking and dynamic acoustic resistance adjusting of porous, sintered metal disc-type resistors mechanically fed to and seated within pre-formed apertures in the armature-supporting frame of carbon type telephone transmitter or central armature type receiver units. At a &#39;&#39;&#39;&#39;sensing&#39;&#39;&#39;&#39; station, air flow is established through each acoustic resistor previously positioned within a pre-formed aperture of the frame, and the total resultant back pressure is measured, with the magnitude thereof being used as a control parameter in a fluidic circuit to determine the presence or absence, as well as acceptable or unacceptable position, of one or more resistors which should have pre-viously been seated in the frame. At the &#39;&#39;&#39;&#39;staking&#39;&#39;&#39;&#39; station, the magnitude of a similarly established back pressure is utilized as a control parameter in the fluidic circuit to determine the particular degree of force which should be applied to each resistor by the staking punches during each staking operation. This permits the air flow resistance exhibited by the resistors staked in each frame to be dynamically adjusted within very close limits, regardless of any physical variations that may exist between such resistors as manufactured. Memory circuitry within the fluidic circuit stores information received from both the sensing and staking stations and provides delayed output control signals for selectively operating frame ejection apparatus employed at Accept or Reject stations associated with, but removed from, the sensing and staking stations, respectively.

United States Patent Meyers et al.

[151 3,704,502 [451 Dec. 5, 1972 [54] APPARATUS FOR'FLUIDICALLY CONTROLLING THE ASSEMBLY AND DYNAMIC RESISTANCE ADJUSTMENT OF ACOUSTIC RESISTORS [72] Inventors: Benjamin F. Meyers, Indianapolis, lnd.; John E. Oldis, Jr., Titusville,

[73] Assignee: Western Electric Company, Incorporated, New York, N.Y.

22 Filed: June 25, 1970 211 Appl. No.: 49,636

[52] US. Cl. ..29/203 R, 29/208 C, 29/208 D [51] Int. Cl ..I-I0lr [58] Field of Search.29/203 R, 208 D, 208 C, 200 A,

29/407, 200 P, 203 P, 208 E Primary Examiner-Charles W. Lanham Assistant Examiner-Victor A. DiPalma Attorney-W. M. Kain, R. P. Miller and A. C.

Schwarz, Jr.

[5 7] ABSTRACT A method of and apparatus for fluidically controlling V the sensing, staking and dynamic acoustic resistance adjusting of porous, sintered metal disc-type resistors mechanically fed to and seated within pre-formed apertures in the armature-supporting frame of carbon type telephone transmitter or central armature type receiver units. At a sensing station, air flow is established through each acoustic resistor previously positioned within a pre-formed aperture of the frame, and the total resultant back pressure is measured, with the magnitude thereof being used as a control parameter in a fluidic circuit to determine the presence or absence, as well as acceptable or unacceptable position, of one or more resistors which should have previously been seated in the frame. At the staking station, the magnitude of a similarly established back pressure is utilized as a control parameter in the fluidic circuit to determine the particular degree of force which should be applied to each resistor by the staking punches during each staking operation. This permits the air flow resistance exhibited by the resistors staked in each frame to be dynamically adjusted within very close limits, regardless of any physical variations that may exist between such resistors as manufactured. Memory circuitry within the fluidic circuit stores information received from both the sensing and staking stations and provides delayed output control signals for selectively operating frame ejection apparatus employed at Accept or Reject stations associated with, but removed from, the sensing and staking stations, respectively.

11 Claims, 26 Drawing Figures PATENTEDBEC 5:912

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PATENTED DEC 5 I972 SHEET IOUF 12 $6.: M3222 or rd m APPARATUS FOR FLUIDICALLY CONTROLLING THE ASSEMBLY AND DYNAMIC RESISTANCE ADJUSTMENT OF ACOUSTIC RESISTORS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the manufacture of electrical transducers and, more particularly, to carbon type transmitter and/or central armature type receiver units which are employed in telephones. These units utilize disc-shaped acoustic resistors, generally formed of sintered metallic material of controlled porosity, staked within preformedapertures of a frame member thereof. Such air-flow resistors act as damping devices to limit the degree of physical displacement of the transmitter or receiver diaphragm during normal operation.

It should be understood that the words acoustic resistor, acoustic disc or air-flow resistor as used hereinafter are intended to encompass air-flow membranes in general, be they of sintered metallic material or of metallic or non-metallic materials in other forms, and with it being further understood that such membranes may be formed into many shapes other than discs, and used in other applications and for other purposes than those disclosed herein.

2. Description of the Prior Art ln assembling disc-type, sintered metal acoustic resistors within pre-formed apertures in the frame of telephone transmitter or receiver units, a staking operation is required. As such resistors are generally manufactured with a resistance-dependent degree of porosity which is intended to be uniform, any pressure exerted on the resistors which would alter their porosity during the staking operation will quite naturally alter their as-received value of resistance.

Accordingly, in an attempt to achieve consistent staked acoustic resistance values heretofore, great care had been taken in the design of the staking tools and holding fixtures. Unfortunately, however, the resultant acoustic resistance of such resistors, as measured after assembly, was found to vary quite widely on either side of an acceptable range therefor. Investigation revealed that in many cases this resulted from variations in how the resistors were initially seated in the pre-formed undercut apertures of the frame. Improper seating, of course, could alter the spacing between a given resistor and a staking punch and this, in turn, could adversely lead to variations in the amount of metal moved by the punch during a staking operation. In addition, it was found that variations in the final value of acoustic resistance exhibited by the resistors was also due to variations in the size and/or porosity (or alternatively, density) of the sintered disc-type resistors as manufactured.

Unfortunately, the aforementioned variable factors negated any possibility of staking disc-type acoustic resistors with a nominal staking punch force and/or driving stroke, whereby all of the resistors would consistently exhibit a nominal value of acoustic resistance, or fall within an acceptable range of resistances, on a large volume production basis. Moreover, those staked resistors which were subsequently found to be defective necessitated that not only they be scrapped, but also the associated frame in which they were staked.

Such total scrapping was necessary, heretofore, because the actual measurement of acoustic resistance could only be determined following the staking operation. As such, both the staking and testing operations heretofore were essentially static operations. More specifically, with respect to the staking operation, a predetermined nominal staking force and driving stroke were usually employed. As for measuring the acoustic resistance, this was similarly a static test in the sense that it simply involved measuring the as staked value of acoustic resistance, with there being no practical way to alter it. Moreover, the problems encoun tered heretofore in obtaining acceptable, finally staked acoustic resistors were further compounded by the airto-electric and electric-to-air interface devices required in the measuring apparatus.

More specifically, a diaphragm-actuated pressure switch was utilized to indicate the value of acoustic re sistance exhibited by each resistor, or more generally of several resistors in combination in a given frame, with the actual deflection of the diaphragm being utilized to operate electrical contacts of the pressure switch at some predetermined chosen point of diaphragm deflection. Limited diaphragm and switch contact life, unreliable repeatability of the deflection distance vs. pressure characteristics over extended periods and high hysteresis all contributed to the undesirability of using such test apparatus in a high production application. in addition, since air was the medium being used in the actual test, and since air was the medium being used in the power portion of the testing operation, it intuitively seemed to be undesirable to test in air, perform the logic electrically, and then provide the power with air. This reasoning has proved to be correct, at least when applied to the practical application disclosed herein.

SUMMARY OF THE INVENTION An object of the present invention is to provide a new method of and apparatus for fluidically controlling the assembly of an air flow membrane within an aperture of a supporting structure, and to dynamically adjust the air flow resistance exhibited by the membrane during assembly.

It is another object of this invention to provide a new method of and apparatus for fluidically controlling the staking and acoustic resistance adjusting of porous, disc-type acoustic resistors within pre-formed apertures in the frames of carbon type telephone transmitter and central armature type receiver units, with the acoustic resistance of such units being adjusted dynamically to an optimum value or within an acceptable range while the staking operation is in progress.

it is a further object of this invention to provide a new and improved apparatus for assembling disc-type acoustic resistors in associated frames of telephone transmitter and receiver units, which apparatus is of simplified, rugged and reliable construction, and is operated on a completely automated, high volume production line basis.

in accordance with one particular application employing a preferred method and structural embodiment of the invention, two porous, sintered metal acoustic resistors, in the form of discs, are fed to and loosely positioned within undercut, pre-formed apertures of a cylindrical frame comprising part of a carbon type telephone transmitter unit. Thereafter, the resistors are sensed under the control of a fluidic circuit for their presence and proper positioning, and then staked within the associated apertures of the frame under a fluidically controlled staking force. This allows the value of acoustic resistance of the resistors to be dynamically adjusted simultaneously and in conjunction with the staking operation.

At the sensing station, air is supplied to the disctype acoustic resistors previously seated in the transmitter frame through a pair of hollow tubes, the terminating ends of which respectively surround the pair of pre-formed apertures in the frame. The combined back pressure developed in both tubes is continuously monitored during the time each frame is located at the sensing station. If the resultant magnitude of the back pressure should indicate that one or both acoustic resistors are missing or are improperly nested within an associated aperture, that sensed condition is utilized as a control parameter to thereafter effect the ejection of that particular frame from the nest feeding conveyor.

At the staking station, hollow staking punches are utilized to supply air to the respective acoustic resistors previously mounted within the particular aligned frame, and the magnitude of the back pressure is again continuously monitored while at that station and during the staking operation. Significantly, the magnitude of this monitored back pressure is again utilized as a control parameter to determine the degree of force which should be applied to the staking punches. Advantageously, this permits the acoustic resistance of each resistor, or alternatively of a pair of resistors associated with each staking head in the illustrative embodiment, to be dynamically adjusted within very close limits, regardless of any physical variations that may exist between the porous disc-type resistors as manufactured.

In accordance with one preferred embodiment of the invention, the apparatus includes a nest feeding conveyor and an in-line array of operating stations including a frame loading station, a frame orienting station, a resistor loading station, a resistor pre-inspect (or sensing) station, a resistor reject-accept station, a resistor staking station and a staked resistor reject-accept station.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1, comprised of FIGS. 1A and 1B, is a plan view of the composite apparatus employed to initially position and then stake disc-type acoustic resistors in the frame of transmitter and/or receiver telephone units, and during the staking operation to simultaneously dynamically adjust the resistance of such resistors on an automated basis in accordance with the principles of the present invention;

FIG. 2 is an enlarged plan view of a portion of the frame loading station of the apparatus;

FIG. 3 is a sectional view of that portion of the composite apparatus depicted in FIG. 1A taken along the line 33 thereof;

FIG. 4 is a sectional view of that portion of the composite apparatus illustrated in FIG. 2 taken along the line 4-4 thereof;

FIG. 5 is a perspective view of a frame for a typical telephone transmitter unit having a central aperture and two mutually disposed apertures with undercut shoulders formed therein, and further illustrating two disc-type acoustic resistors seated and staked within the outer apertures in accordance with the principles of the present invention;

FIG. 6 is a side elevational view, partially in section, of one of two identical mechanisms associated with the common frame orienting station for providing accurate rotational positioning of each frame within a nest after having been advanced thereto;

FIG. 7 is an enlarged, partial sectional view taken along the line 77 of FIG. 6, and discloses certain movable details of the operating head of one of the frame orienting mechanisms, and of the position thereof relative to a transmitter or receiver frame loosely positioned within a nest associated with the conveyor of the composite apparatus;

FIG. 8 is an enlarged, partial plan view taken along the line 8-8 of FIG. 7 of several nests and frames positioned on the conveyor, and. illustrating in greater detail the structure of the conveyor; I

FIG. 9 is a partial plan view of one of two identical mechanisms associated with the common acoustic resistor loading station, and illustrates, in particular, apparatus for feeding disc-type resistors to and properly positioning them within the respectively aligned undercut apertures of each transmitter or receiver frame advanced to that station in a nest of the conveyor;

FIG. MB is a partial detail view of one of the two identical resistor loading heads;

FIG. 11 is a partial sectional detail view of one of the two feed tubes associated with a common resistor loading head after it has moved downwardly so as to position the terminating end of the feed tube coaxia'lly of an aligned aperture in a frame, and further discloses a disc-type resistor, in phantom, being dropped by gravity feed downwardly through and toward the terminat ing end of the feed tube, and the same resistor in crosssection after having been seated in the frame;

FIG. 12 is a side elevational view, partially in section, of one of two identical mechanisms associated with the common resistor sensing (or pre-inspect) station, and particularly illustrates the apparatus for determining whether or not two acoustic resistors were fed to and properly positioned within the respective undercut apertures of each frame of a transmitter or receiver unit prior to having been advanced to the sensing station in accordance with the principles of the present invention;

FIG. 13 is a detail side elevational view, partially in section, illustrating the relationship between one sensing head frame, two seated acoustic resistors and an associated nest during a sensing operation;

FIG. M is a partial detail view in section of the apparatus employed at the resistor accept reject station, and which apparatus is duplicated at the staked-resistor accept-reject station;

FIG. 15 is a partial, side elevational view of one of two identical staking mechanisms associated with the common staking station, and particularly illustrates the apparatus utilized for driving a pair of staking punches downwardly against the frame of a transmitter or receiver unit so as to stake previously seated acoustic disc-type resistors within the aligned apertures of the frame;

FIG. 16 is a detail side elevational view of one staking punch, a portion of both the frame and the supporting nest aligned therewith, and of a resistor after having been staked within an aperture of the frame in accordance with the principles of the present invention;

FIG. 17 is a graph illustrating the differential pressure vs. flow-constant for a generator of the type embodied in the fluidic circuit of the present invention;

FIG. 18 is a schematic logic diagram illustrating in simplified form a constant-flow generator and the pressure sensing portion of the fluidic circuit associated with the sensing station;

FIG. 19 is a simplified schematic logic diagram illustrating certain of the basic fluidic devices and the functions performed thereby in the composite fluidic control circuitry embodied in the present invention;

FIG. 20 is a timing chart indicating when the various work stations are operated during the operating cycle;

FIG.- 21 is a schematic diagram of the composite fluidic circuit which controls many of the operations performed by the composite apparatus at the various work stations in accordance with the present invention; and

FIG. 22, comprises of FIGS. 22A and 22B, is a schematic circuit diagram illustrating the composite fluidic circuit in greater detail, FIG. 22A illustrating the schematic circuitry associated with the two sensing (or preinspect) heads employed at the common sensing station, together with the cam-controlled sensors employed in conjunction with the composite circuit, and FIG. 22B illustrating the fluidic control circuits associated with the two staking-acoustic resistance adjusting heads, as embodied in the present invention.

DETAILED DESCRIPTION Description of Product Assembled In describing in greater detail the method of and apparatus embodied in the present invention, reference will be made to a specific manufacturing application involving the staking of disc-shaped acoustic resistors 26 (see FIG. 5) within pre-formed, undercut apertures 27 of a cylindrical frame 28 of either a telephone handset transmitter or receiver unit. One typical handset, for example, utilizes five acoustic resistors, two in the transmitter unit and three in the receiver unit.

The acoustic resistors are normally made of sintered stainless steel, and compressed into the desired shape under controlled conditions which are intended to result in all of the resistors exhibiting a consistent degree of porosity (or density) as manufactured. As previously mentioned, however, this result is hardly ever achieved in actual practice. Compounding the problem of controlling the porosity of the resistors, of course, is the necessity to stake them within the supporting frame. This staking operation has heretofore often resulted in the porosity dependent air flow resistance of the resistors varying appreciably, and in many cases beyond acceptable limits.

With respect to the transmitter frame 28, it is normally made of a zinc alloy, and has, in addition to the two resistor-receiving apertures 27, a larger central aperture 27a which accommodates a carbon filled transducer assembly (not shown).

When the acoustic resistors are staked within a transmitter frame (that combination generally being referred to as a T-l bridge in connection with one par- OVERALL DESCRIPTION OF COMPOSITE MECHANICAL APPARATUS Before considering the fluidic control circuit in detail, attention will first be directed to the details of the composite apparatus and, in particular, the sensing and staking stations thereof, which operate under the control of the fluidic circuit.

In accordance with one illustrative embodiment of the present invention depicted in FIGS. 1A and 1B, the composite apparatus 30 comprises a nest feeding conveyor 31 and an in-line array of operating stations in cluding a frame loading station designated generally by the reference numeral 40, a frame orienting station 150, a disc-type acoustic resistor loading station 220, a resistor sensing station 270, a resistor reject-accept station 320, a resistor staking station 360, and a staked-resistor-frame reject-accept station 380. The entire apparatus is supported on a main base member 32.

FRAME LOADING STATION Considering now in greater detail the frame loading station 40 best seen in FIGS. 1A and 2-4, transmitter frames 28 (FIG. 5 such as of the type employed in one particular telephone handset, are successively fed from either one of two conventional vibratory supply bowls 33a,b into an associated stationary feed track 34a,b.

Associated with the feed track 34a is a first crossslide mechanism which comprises a first cam-operated cross-slide member 41 (see FIGS. 1A and 2) secured to a retractable drive rod 43. The drive rod is supported within a bore of and slidable relative to a stationary support block 45 which, in turn, is secured to a support member 46 of the apparatus. The end of the drive rod 43 opposite the cross-slide member 41 (see FIG. 1A) has a rotatable cam follower 47 secured thereto which biases against an eccentric cam 48 secured to a rotatable main cam shaft 51. The cam follower is spring biased against the eccentric cam 48 by means of a coil spring 53 which is supported at one end to the support block 45 and at the other end to the cross-slide member end of the drive rod 43.

A retractable nest-aligning pin 55 (best seen in FIGS. 2 and 3) is also supported within a bore of and slidable relative to a channel plate member 56 (FIG. 3). The nest aligning pin is secured through a coil spring 57 (FIG. 3) to a connecting rod 58, the latter being supported within and slidable relative to a bore extending through the support block 45 (FIG. 1A). One end of the connecting rod 58 has a rotatable cam follower 59 secured thereto, the latter being held in contactingrelationship with a cam 61 secured to the drive shaft 51 by means of the coil spring 57. The function of the nest aligning pin will become more apparent hereinbelow in connection with a description of both the nests carried by the conveyor and of the operation of the composite frame loading apparatus.

As best seen in FIG. 2, a spring-biased escapement mechanism 65 comprises a lever 66 secured to a bifurcated member 67, with the latter being pivotally secured to the channel plate member 56 of the apparatus by means of a pin 68. An adjustable contact member 69 is secured to the lower end' of a lever 66. Upon retraction of the drive rod 43, the back edge of the cross-slide member 41 makes contact with the adjustable contact member 69 of the ejection mechanism. This causes the lever to pivot upwardly into a horizontal position, thereby compressing a coil spring 71 coaxially positioned about a pin 72 pivotally secured at its lower end to the lever 66 and at its upper end to a stationary bracket 73 of the apparatus.

As best seen in FIG. 2, when the lever is spring biased toward a nest 78, the nose portion 67a of the bifurcated member provides a temporary stop for the end frame 28a positioned in the associated stationary feed track 34. When the lever 66 is spring biased into a horizontal position, however, the nose portion 67a releases the end frame and the nose portion 67b momentarily functions as the stop for the next succeeding frame which is now the end one. Upon the lever of the escapement mechanism again being spring biased toward a nest, the nose portion 67a again functions as the stop for the end frame previously retained by the nose portion 67b.

Each frame upon being released by the escapement mechanism 65 is moved from the position designated 28a in FIGS. 1A and 2 to the position 28a by gravity feed down the inclined portion 34a of the feed track. An L-shaped stop member 76, secured to a stationary support plate 77 (FIGS. 2,3) of the apparatus, is positioned in aligned relationship with the cross-slide member 41. As such, when the cross-slide is moved so as to transport a frame 28 from the position designated 28a in FIG. 1A to the position designated 28a", the combination of the cross-slide member 41 and the stop member 76 results in the transported frame being accurately positioned within an aligned nest 78 of the conveyor, best seen in FIGS. 3 and 4. The inner frame confining edges of both the cross-slide member 41 and the stationary stop member 76 have undercut grooves formed therein so as to accommodate the projecting flange portion of the frame 28.

A second cam-operated cross-slide mechanism associated with the feed track 34b comprises a cross-slide member 81 (best seen in FIGS. 1A and 2) which is secured to a retractable drive rod 83 which, in turn, is supported within a bore of and slidable relative to a stationary block 85. The end of the drive rod 83 opposite the cross-slide member 81 is connected by means of a pin 86 to a rotatable cam follower 88 which, in turn, is held in contacting relationship with an eccentric cam 91 secured to the drive shaft 51. A coil spring 93, affixed at one end to the drive rod 83 and at the other end to the stationary block 85, maintains the cam follower in continuous contacting relationship with the cam 91.

A retractable spring-biased nest aligning pin 96 (FIG. 2), identical to the pin 55 previously described, is also supported within a bore of and slidable relative to the channel plate member 56 (FIGS. 2 and 3). The nest aligning pin 96 is secured through a coil spring (not shown but identical to the spring 57 depicted in FIG. 3)

to a connecting rod 97, the latter being supported within and slidable relative to a bore extending through the support block 85. One end of the connectingrod 97 has a rotatable cam follower 98 secured thereto, the latter being held in contacting relationship with a cam 99 secured to the drive shaft 51 by means of the aforementioned coil spring, not shown.

Associated with the cross-slide member 81 is a stationary stop member (best seen in FIG. 2), the combination insuring that each successiveframe 28 will be accurately positioned in an aligned nesting fixture 78 of the conveyor. Both the cross-slide member 81 and the stop member 105 have undercut grooves therein so as to accommodate the projecting flange portion of each frame 28. Cross-slide member 41, primarily associated with feed track 34a, also has an undercut groove along the edge nearest the stop member 185 so as to provide further confinement of a frame transported by the cross-slide member 81 into an aligned nest of the conveyor.

A second escapement mechanism (FIG. 1A), which is constructed and operates in the same manner as the escapement mechanism 65 described hereinabove, is similarly pivotally mounted on the channel plate member 77 of the apparatus and successively releases frames 28 from the stationary guide track 34b in response to the reciprocal movement of the cross-slide 81.

CONVEYOR MECHANISM As best seenin FIGS. 3 and 8, the conveyor 31 comprises two parallel extendinglink-chains 112, with a spaced array of the nests 78 supported therebetween. The intermediate shank portion of pins 113 of each chain-link rides along a slot 114 defined by two mutually disposed leg portions of mating rail blocks 115a and b associated with each chain (see FIG. 3). The two pair of parallel extending rail blocks are secured to a base plate 140. The link-chains engage a pair of sprocket wheels (not shown) at each end of a closed loop, with the downstream sprocket wheel being secured to a drive shaft 122 (FIG. 1B) which, in turn, is coupled through a chain drive coupler unit designated generally by the reference numeral 125 to a clutch unit 126. The clutch unit is connected through a gear reducer 127 to a composite motor-clutch-brake power source designated 129. As also best seen in FIG. 1B, the drive shaft 51 is chain-drive coupled to the clutch mechanism 126.

Each nest 78 of the conveyor, as best seen in FIGS. 3 and 8, comprises a substantially U-shaped block which has a central bore extending therethrough and within which is positioned for slidable movement relative thereto a double-headed biasing member 137. Two additional bores are also formed in the U-slraped block 135, which bores respectively accommodate coil springs 138 and the head portions of the alignment pins 141.

The under-surface of the upper head portion of each biasing pin 137 normally makes contact with the two adjacent head portions of the orienting pins 138 as best seen in FIG. 3. The lower head portion of each biasing pin 137 rides within a groove formed by two juxtaposed stationary cam members 139, the latter being secured to the lower base plate 140 of the apparatus. The stationar'y cam members 139, only one of which is seen in FIG. 4,, provice a means whereby the biasing pin 137 associated with each nest may be moved up and down relative thereto during longitudinal movement of the conveyor. Such movement of the pin 137, in turn, moves the spring-biased orienting pins 141 controllably into and out of the aligned apertures of a particular frame 28, previously positioned within an associated nest 78 of the conveyor. The reasons for such movement of the orienting pins will be discussed in greater detail hereinafter.

In order to insure accurate alignment of each nest at each work station, the U-shaped block 135 thereof is formed with a keying slot 135a in one side, and is secured to the chain conveyor through a pair of cylindrical members 143 (see FIGS. 3 and 8), each being secured to a separate bracket 145. Each bracket is, in turn, secured to a pair of pins 113 of and functions as a link of the chain conveyor. A pair of mutually disposed stop plates 146 (FIG. 8) are secured to the front and back sides of each nest block 135 relative to the directions of movement thereof. Limited spring-biased longitudinal movement of each nest block 135, relative to the cylindrical members 143 and the chain conveyor, is effected through the use of four coil springs 149. These springs are partially disposed within respective bores of the cylindrical members 145, and have their free ends biased against the stop plates 146.

Such spring-biased nest mounting permits each of the aforementioned nest-aligning pins 55 and 96, when advanced, to readily wedge into at least a partially aligned keying notch 135a of a nest block indexed thereto. The alignment pins thereby insure that each nest block is accurately positioned and rigidly clamped at the frame loading work station. As will be seen hereinafter, similar nest aligning pins are also employed at each of the other work stations.

FRAME ORIENTING STATION Upon two frames 28 being positioned within two adjacent and respectively aligned nests 78 of the conveyor at the frame loading station 40, the conveyor is advanced the equivalent of two nest positions whereat, as depicted in FIG. 1A, the two most recently loaded frames are positioned at the frame orienting station 150. When the frames arrive at this station, the acoustic resistor-receiving apertures 27 pre-formed therein may or may not be aligned with the springbiased alignment pins 141 associated with each nest 78. If a given frame should not be properly oriented, the apparatus at the frame orienting station is constructed to rotate either one or both frames advanced to that station until each frame is properly positioned relative to the orienting pins 141.

With particular reference now to FIGS. 6 and 7, and with respect to only one of two identical mechanisms associated with that station, a cam-actuated lever 151 is pivotally supported by a pin 152 which, in turn, is mounted on a U-shaped support bracket 153. The bracket is mounted on a support block 154 which, in turn, is secured to the stationary support member 46.

The lever 151 supports at one end an air motor 155 and at the opposite end a rotatable cam follower 157 which is maintained in contacting relationship with a cam 158 by means of a coil spring 161 supported between the support block 156 and the lever 151. The air motor 155 has mounted on the shaft thereof a resilient pad assembly designated generally by the reference numeral 165. The pad assembly comprises a resilient circular pad 166, such as of rubber, which is supported by a circumferentially disposed array of fastening members 168 which extend through aligned apertures in a spacer plate 171 having a collar portion (as best seen in FIG. 7) which is secured by any suitable means to the shaft of the air motor 155. The pressure pad is spring biased by means of a coil spring 177 which is positioned between the pressure 'pad 166 and a recessed portion of the spacer plate 171.

A triangularly shaped cam follower support plate 187 is pivotally secured by a pin 188'to a bracket 191 affixed to the stationary support member 46. A cam follower 193 is rotatably secured to the plate 187 near one corner thereof, and continuously makes contact with a cam 195 (shown only partially by a dashed line in FIG. 6). Another cam follower 197 is also rotatably secured to the plate 187 and makes contact with a protruding spring-biased push button 198 of a microswitch 199. The microswitch, actuated in response to rotation of the cam 195, is employed to control the time during which theair motor 155 is operated. More specifically, the microswitch 199 operates a conventional solenoid actuated pneumatic valve MV1 which, in turn, controllably supplies air from a manifold MFl, depicted in FIG. 21, to the air motor 155.

Mounted for retractable movement within a passage of the support block 154 is a connecting rod 201. A cam follower 203 is rotatably secured to the rod 201 at one end, and is maintained in contact with a cam 284 (only partially shown by a dashed line) by means of a coil spring 205 which is partially supported within a bore of the support member 46 at one end and abuts against a stop member 206 secured to the driving rod at the other end. A coil spring 209, partially secured within a bore of the connecting rod at the forward end, biases against a nest aligning pin 211, the head portion of which is best seen in FIG. 8.

A stop member 213, secured to a forward nose portion of the connecting rod 201, extends into and is capable of travelling along a slot 214 in the aligning pin 211. Member 213 normally is spring-biased against the rearward end of the slot during the forward travel of the pin 211 unless an obstruction should be encountered by the latter. Pin 211, as in the case with pins 55 and 96 associated with the frame loading station (FIG. 2), projects through an aperture in the rail block b after each indexing of a nest into alignment therewith, and further wedges into the notched area a of the nest block 135 so as to accurately and firmly position the latter at that work station. As previously mentioned, all of the nests 78 are spring mounted relative to the conveyor 31 by means of the four coil springs 149 so as to facilitate the attainment of accurate nest positioning.

With respect to the operation of the frame orienting apparatus 150, the cam 158 (best seen in FIG. 6) initially effects pivotal movement of the lever 151 through the cam follower 157 so that the resilient pressure pad 166 connected to the air motor makes contact with the upper surface of an aligned frame 28 supported by a particular nest 78 indexed into aligned relationship with the air motor. Just prior to such contact, the microswitch 199 is actuated to in turn operated the air motor which causes the resilient pad to rotate the particular frame a sufficient number of degrees, which may be a fractional part of one revolution or several revolutions, until the spring-biased alignment pins 141 (see FIG. 3) associated with the particular aligned nest snap upwardly through the pre-formed acoustic resistor apertures 27 in the frame 28.

Normally after two or three revolutions of the resilient pad, the particular number of revolutions being readily controllable by either the cam 195, or by other independent timing means of conventional design, the spring-biased lever 151 is pivoted such that the air motor 155 and resilient pad 166 secured thereto are raised above the correctly oriented frame. During the period in which contact is maintained between the pressure pad 166 and a frame 28 aligned therewith, cam 204, through the cam follower 203 and the connecting rod 201, forces the aligning pin 211 into the notch 135a of the aligned nest.

RESISTOR LOADING STATION Upon indexing of the conveyor two more nest positions, the nests previously located at the frame orienting station 150 are now positioned at an acoustic resistor-loading station designated generally by the reference numeral 220 (see FIG. 1B). As the resistorloading apparatus associated with each of the two nests at this station is identical, the apparatus associated with only one nest will be disclosed in detail and described hereinafter. At this station, the acoustic resistor apertures 27 of each frame 28 are respectively aligned with two hollow acoustic-resistor feed tubes 222 (see FIGS. 9-11). These feed tubes are slidably supported within bores of a connector block 223 which, in turn, is secured to a pivotal lever 255 (see FIGS. 18,10).

As in the case of the lever 151 described hereinabove in connection with the frame orienting station, each lever 225 is pivoted about a pin 227 (FIG. 1B) supported on a support block 229. Block 229 is, in turn, secured to the stationary support plate 46 of the apparatus. As also seen in FIG. 1B, pivotal movement of each lever 225 is effected through a common cam follower 231 which is maintained in contacting relationship with a common cam 232 secured to the drive shaft 51. A coil spring, not shown but similar to spring 161 employed at the frame orienting station and depicted in FIG. 6, biases each cam follower 231 against the cam 232.

A pair of nest aligning pins, not shown but similar to the pins 211 depicted in FIG. 8, are employed at the disc loading station and are reciprocally moved by the respective connecting rods 234 illustrated in FIG. 18. Each connecting rod is operated through a cam follower 235 and an associated cam 236, the latter being connected to the drive shaft 51.

Each hollow feed tube 222 at the disc loading station, as best seen in FIGS. 10 and 11,v is mounted for spring-biased movement within'an associated bore of the connector block 223 by means of a coil spring 237, with the relative displacement between the feed tube and the block being confined between two spaced stop members 239 secured to the feed tube. The lower end I of each feed tube comprises a tapered conical nose portion 241 (see FIG. 11) which is dimensioned so as to coaxially surround an aligned one of the two apertures 27 formed in each frame.

Acoustic disc-type resistors 26 are successively fed from a vibratory supply bowl 242 to an aligned frame 28 through the hollow feed tubes 222 (best seen in FIG. 9). An escapement mechanism, designated generally by the reference numeral 245, is utilized to feed'only one acoustic resistor down each feed tube 222 during each dwell period of the indexible conveyor.

The ejection mechanism 245 accomplishes this result through the utilization of a pair of pivotal levers 247 respectively associated with the two feed tubes 222. With reference to the apparatus associated with only one feed tube, as such apparatus is identical for the other feed tube, the lower lever in FIG. 9, for example, is pivotally secured at an intermediate point to a pin 248, the latter being secured to a stationary bracket 249. This lever is actuated by means of a piston of a pneumatic feed cylinder FCl coupled to one end thereof by means of a pin 253. The opposite end of lever 247 is bifurcated and drives a pin 254 of a crossslide 255 in a reciprocal manner, as illustrated by one position of lever 247 and the associated cross-slide being shown in phantom in FIG. 9.

The cross-slide 255 has a notch 257 formed therein which is dimensioned to receive one acoustic disc-type resistor 26 fed thereto by gravity feed from the feed track 244 of the supply bowl. Upon actuation of the lever 247 by means of the pneumatic cylinder FC1, an acoustic resistor deposited in the notch 257 of the cross-slide is transported by the latter to a position over the upper end of an associated feed tube 222 whereupon it falls by gravity, as indicated in phantom in FIG. 11, to and within the aligned aperture 27 (FIG. 5) of a given frame 28.

In order to allow the resistors to be seated within the respective apertures of each frame indexed to the resistor loading station, the alignment pins 141 of each aligned nest are withdrawn downwardly into the nest block while positioned at that station. This is accomplished with a cam member (not shown) which is identical to the one designated 139 in FIG. 4. As previously mentioned, this cam member causes the doubleheaded member 137 associated with each nest indexed to the resistor loading station 2210 to force the alignment pins 141 downwardly by a distance sufficient to present no obstruction with the apertures 27 of a given aligned frame 28, best seen in FIG. 10.

Primarily because of the area required for each resistor loading mechanism associated with a different aligned frame, the common resistor loading station 220 actually comprises two mechanisms of the type depicted in FIG. 9 separated by two nest positions as depicted in FIG. 1B. As such, while two frame-carrying nests 78 are positioned beneath each supply bowl 242 during each indexing dwell period, as illustrated in FIG. 13, two acoustic resistors are actually fed to only one of the frames under each supply bowl. In order to load successive frames transported along the conveyor with acoustic disc-type resistors, the first supply bowl, as seen in FIG. 1B, loads the first (or upstream) frame positioned therebeneath whereas the second vibratory bowl loads the second (or downstream) frame during the dwell period between each indexing of the conveyor two nest positions.

LOADED RESISTOR SENSING STATION Upon two acoustic disc-type resistors having been deposited (or at least time having been allowed for their being deposited) within the appropriate apertures of every frame passed through the resistor loading station, such loaded frames are indexed in adjacent pairs to an acoustic resistor sensing or pre-inspect station 270 (FIGS. 18, 12 and 13). In accordance with the principles of the present invention, two sensing heads designated generally by the reference numeral-27S and respectively associated with a different resistor-loaded frame assembly, are employed in establishing and measuring the magnitude of back pressure developed as a result of a controllable amount of air being directed through the acoustic resistors of an associated frame. The particular magnitude of the measured back pressure is utilized in a fluidic circuit, to be described in greater detail hereinbelow, to sense whether or not all of the resistors of a given frame are present and if they are, to further sense whether or not they are properly positioned in the frame. This information is temporarily stored, in logic form, in the fluidic circuit and subsequently used as a control signal at a subsequent resistor-loaded accept-reject station 350.

Considering one of the two identical sensing heads 275 now in greater detail (FIGS. 12,13), it includes two tapered conical members 277, each having an axial aperture extending therethrough which communicates with a different air passage 281 formed in a connector block 282. The air passages 281 are connected to a common inlet air line 285.

Each sensing head 275, through the connector block 283, is secured by any suitable means to one end of a pivotal lever 287. An intermediate region of the lever and one end of a member 289 are pivotally secured to a pin 291 which is connected to a bracket 293. The bracket, in turn, is connected indirectly to the common stationary support plate 46 through a' support block 295. 1

The end of the member 289 opposite the pivot end has a cam follower 297 secured thereto which continuously contacts a lever-pivoting cam 298, and is held in spring-biased relationship therewith by means of a coil spring 299 interposed between the support block 295 and the lever 287. A coil spring 301, supported by a fastener 302, exerts a downward force on an intermediate region of the member 289 and a mating end region of the pivotal lever 287 so as to allow the lever to pivot relative to the member 289 should the sensing head 275 hit an obstruction in being lowered against an aligned frame.

A biasing pin 303, secured to and extending downwardly from the connector block 282, projects through the central aperture 26a in each frame 28 aligned therewith when the sensing head is moved downwardly against the frame. The pin 303 is employed to bias against the double-headed member 137 so as to, in turn, overcome the spring bias of the alignment pins 141 and thereby move the latter downwardly out of engagement with the acoustic resistor apertures of the frame. This is done to allow air to be directed through the acoustic resistors during the sensing operation.

In order to remove some of the downward force which would be exerted on the conveyor chain 113 by reason of the pin 303, successive nests 78 ride along a short longitudinal section of track, comprising two spaced members 304 which are secured at their lower ends to the support plate 140.

A nest aligning pin 305 is associated with each sensing head, and is actuated by a spring-biased connecting rod 306 which is positioned within a passage of and slidable relative to the support block 295. One end of the rod 306 has a cam follower 307 rotatably secured thereto which continuously makes contact with a cam 308. The other end of the drive rod biases against a coil spring 309 which, in turn, biases against the nest aligning pin 305. Pin 305 slidably extends through a bore formed in the common conveyor rail block 115b, and is utilized to accurately and rigidly position a given nest 78 in aligned relationship with respect to an associated one of the two sensing heads 275 at the sensing station 270. I

A stop member 312, secured to the connecting rod 306, extends into and is capable of travelling along a slot 305a in the aligning pin 305. Member 312nonnally is spring-biased against the rearward end of the slot during the longitudinal movement of the pin in response to the cam-actuated movement of the connecting rod. A coil spring 313, partially positioned within a bore of the stationary base 46, continuously biases against a stop 315 secured to the connecting rod 306 so as to maintain the cam follower 307 in continuous spring-biased contact with the cam 308.

LOADED RESISTOR ACCEPT-REJECT STATION After the sensing heads 275 have been operated in the allotted time under the control of the associated cams 298, the conveyor 31 is' indexed two more nest positions. At this point, the two previously sensed or pre-inspected resistor-loaded frames in adjacent nests are respectively aligned with apparatus comprising a loaded resistor accept-reject station designated generally by the reference numeral 320 (see FIG. 1B). The apparatus associated with only one of the two aligned nests at this station is shown in detail in FIG. 14, and includes a reject cylinder RC1, operated under the control of the fluidic circuit, a blast-off air line 321 and a chute 323. A rigid and clamped terminating end portion 321 of the air line is positioned adjacent to and directed toward one edge of a particular frame 28 when elevated slightly above a normally supporting surface of the aligned nest. With the chute being positioned on the side of the frame opposite the air line portion 32la,an air blast directed at the elevated frame from the air line 321 will lift the frame from the nest and deposit it in the chute. Air is supplied to each of the lines 321 from the feeder line 483 connected to the supply junction point 482 depicted in 1 16.21.

Each reject cylinder, such as RC1, is employed to elevate and thereby facilitate the removal of a defective frame from a given nest positioned at the accept-reject station. This is accomplished by the spring-return piston of the reject cylinder when operated moving upwardly the double-headed biasing member 137 of the 

1. Apparatus for assembling a first part having at least one second part-receiving aperture therein with a second part exhibiting a compressive force-dependent density and a densitydependent resistance to the transmission of a flowable medium therethrough, comprising: first means for forcibly securing by material flow at least one second part within an associated aperture of said first part; second means for producing and directing at least a portion of a flowable medium through said second part, and third means responsive to the magnitude of said flowable medium for controlling the force exerted upon said first and second parts by said first means so that the density-dependent resistance exhibited by said second part to the transmission of said flowable medium therethrough may be controlled within a predetermined range.
 2. Apparatus in accordance with claim 1 wherein said third means includes a fluidic circuit responsive to the back pressure established By the resistance exhibited by said second part to the transmission of said flowable medium therethrough during the securement thereof within the aperture of said first part, said fluidic circuit further including means for generating a signal indicative of an unacceptable securement of a first part-second part assembly whenever the measured magnitude of back pressure does not fall within said predetermined range.
 3. Apparatus in accordance with claim 2 wherein said first securing means comprises a pressure source and a piston driven pneumatically controlled cylinder, said piston supporting and driving securing punches corresponding in number with the second part receiving apertures formed in said first part, and wherein the actuating pressure supplied to said pneumatic cylinder is under the variably timed control of said fluidic circuit.
 4. Apparatus for assembling first and second piece parts wherein said second piece part is of a porous nature allowing at least partial transmission of a flowable medium therethrough, comprising: an indexible nest carrying conveyor for transporting a succession of piece part receiving nests secured therealong to a succession of work stations; a first loading station including means for positioning first parts each having at least one second piece part receiving aperture therein in respective nests advanced by said conveyor to a position in alignment therewith; a second loading station including means for successively feeding a number of said second parts corresponding in number to the receiving apertures in said first part to and in seating relationship with said apertures; a pre-inspect station including means for sensing for the presence of and whether each of said second parts has been properly seated within a given aperture of said first part, and for generating a control signal in the event that a first part of said associated second parts have not been initially properly positioned relative to each other; a staking station including force controllable staking means for permanently securing properly positioned second parts within the respective receiving apertures of said first part, and for generating a control signal in the event that said first and second parts have not been satisfactorily staked, and means responsive to a control signal from either said pre-inspect station or said staking station for ejecting from a given nest of said conveyor any first part-second part assembly which resulted in the generation of a control signal.
 5. Apparatus in accordance with claim 4 wherein said means at said pre-inspect station for sensing for the presence and proper seating of said second parts relative to an associated first part comprises a fluidic circuit directing a controllable flowable medium to said first part and confined to only those areas where said second parts should normally be seated, and said circuit further including fluidic means for measuring the magnitude of the back pressure established because of the partial resistance exhibited by said second parts to the transmission of said flowable medium therethrough, and for differentiating between satisfactory and unsatisfactory magnitudes of back pressure, and for generating a control signal indicative of first and second piece parts which are not properly assembled loosely in the desired relationship.
 6. Apparatus in accordance with claim 5 wherein said force controllable staking means at said staking station comprises a pressure source and a pneumatically controlled, piston driven staking cylinder, said piston supporting and driving a number of staking punches corresponding in number with the second part-receiving apertures formed in said first part, and further including means for simultaneously establishing and directing a predetermined flowable medium partially through each of said second parts seated within associated apertures of said first part, and for measuring the magnitude of the back pressure established because of thE partial resistance exhibited by said second parts to the transmission of said flowable medium therethrough, the magnitude of said back pressure being utilized as a control parameter to control the pressure applied to said pneumatic cylinder and, thereby, to control the degree of permanent compressive force exerted by said piston driven punches on said first part-second part assembly during the staking operation, and said staking means further including circuit means for generating a control signal in response to a signal from said means for measuring the back pressure whenever a given first part-second part assembly cannot be permanently assembled by the staking operation so as to produce a measured back pressure falling within a predetermined range.
 7. Apparatus in accordance with claim 4 further comprising: an orienting station comprising means for angularly moving each successively loaded first part to a desired position relative to and on an associated nest prior to said second piece parts being seated within respectively aligned apertures of said first part.
 8. Apparatus for positioning and staking acoustic resistors exhibiting a compressive force-dependent density and a density-dependent resistance to the transmission of a flowable medium therethrough in pre-formed apertures of a frame member of an electrical transducer comprising: a nest carrying conveyor for feeding a succession of frame receiving nests secured therealong to a succession of work stations; a frame loading station including means for positioning successive frame members of an electrical transducer into successively advanced and aligned nests during each successive indexing of said conveyor; an acoustic resistor loading station including means for successively feeding a different acoustic resistor into each of said pre-formed apertures of a frame positioned in alignment therewith during each advancement of said conveyor; a resistor staking station including means for staking each acoustic resistor positioned within an associated aperture to said frame, and further including means for simultaneously creating a controllable flow of a predetermined medium through each acoustic resistor seated within a given aperture of said frame, and for monitoring the back pressure established by, and the magnitude of which is dependent on, the resistance exhibited by all of said resistors to the flow of said medium therethrough, the magnitude of said back pressure being utilized as a control parameter to control the degree of force exerted by said staking means against each aligned frame-resistor assembly so as to vary the density of and thereby dynamically adjust the value of acoustic resistance of the staked resistors within a predetermined acceptable range, said resistor staking station further including means for generating a reject control signal in response to a signal from said means for monitoring the back pressure whenever the acoustic resistors cannot be adjusted to a desired value during the staking operation, and a staked-resistor reject-accept station including means responsive to said reject control signal from said acoustic resistor staking station for actuating ejection means to remove a given defective staked resistor-frame assembly from a given nest when indexed to the staked resistor reject-accept station.
 9. Apparatus in accordance with claim 8 wherein said means at said staking station for creating a controllable flow of a predetermined medium and for monitoring the back pressure produced by the presence of the acoustic resistors positioned within an associated frame comprises a fluidic circuit, with said medium comprising air.
 10. Apparatus in accordance with claim 9 further comprising: a frame orienting station including means for angularly moving each of said frames to a desired position relative to and on an associated nest so as to consistently insure that said pre-formed apertures in said frame are in alignment with apparatus associated therewith at eaCh successive work station when advanced thereto.
 11. Apparatus in accordance with claim 8 further comprising: a loaded acoustic resistor sensing station including means for sensing whether all of said acoustic resistors associated with a given frame have been fed to and properly seated within the respective pre-formed apertures of said frame, said sensing means including means for establishing a controllable flow of said predetermined medium through each of said seated acoustic resistors, and for monitoring the resultant back pressure established by the number of said resistors present, said last-mentioned means being capable of differentiating between a condition wherein all of said resistors are present and properly seated within the respective apertures in said frame from a condition wherein said resistors are not all present and properly seated, and for generating a second reject control signal whenever the latter condition exists, and wherein said apparatus further includes a loaded-resistor reject-accept station including means responsive to said second reject control signal from said sensing station for actuating ejection means to remove a given defective sensed loaded resistor-frame assembly from a given nest when indexed to the loaded resistor reject-accept station. 